Vesicular and ulcerative dermatopathy resembling superficial necrolytic dermatitis in captive black rhinoceroses (Diceros bicornis)

A review of sebum in mammals in relation to skin diseases, skin function, and the skin microbiome

Diseases vary among and within species but the causes of this variation can be unclear. Immune responses are an important driver of disease variation, but mechanisms on how the body resists pathogen establishment before activation of immune responses are understudied. Skin surfaces of mammals are the first line of defense against abiotic stressors and pathogens, and skin attributes such as pH, microbiomes, and lipids influence disease outcomes. Sebaceous glands produce sebum composed of multiple types of lipids with species-specific compositions. Sebum affects skin barrier function by contributing to minimizing water loss, supporting thermoregulation, protecting against pathogens, and preventing UV-induced damage. Sebum also affects skin microbiome composition both via its antimicrobial properties, and by providing potential nutrient sources. Intra- and interspecific variation in sebum composition influences skin disease outcomes in humans and domestic mammal species but is not well-characterized in wildlife. We synthesized knowledge on sebum function in mammals in relation to skin diseases and the skin microbiome. We found that sebum composition was described for only 29 live, wild mammalian species. Sebum is important in dermatophilosis, various forms of dermatitis, demodicosis, and potentially white-nose syndrome. Sebum composition likely affects disease susceptibility, as lipid components can have antimicrobial functions against specific pathogens. It is unclear why sebum composition is species-specific, but both phylogeny and environmental effects may drive differences. Our review illustrates the role of mammal sebum function and influence on skin microbes in the context of skin diseases, providing a baseline for future studies to elucidate mechanisms of disease resistance beyond immune responses.

Dermatologic Aspects of Zoo Mammal Medicine

The article deals with the primary aspects of how to maintain healthy integument in zoo mammals and in particular why husbandry-related health problems can occur in general in a zoologic setting. While working with these species we are often faced with diagnostic challenges, which may include a general approach (often requiring anesthesia or medical training), lack of "normal" references, and difficulties, especially if the cutaneous signs are not a primary ailment, but a manifestation of a generalized disease (eg, immune-suppression). The different etiologies of skin problems are discussed with clinical examples.

THE USE OF INTRADERMAL SKIN TESTING AND HYPOSENSITIZATION INJECTIONS TO CONTROL SEASONAL DERMATITIS IN GREATER ONE-HORNED RHINOCEROSES (RHINOCEROS UNICORNIS)

Allergic dermatitis was diagnosed in a 25-yr-old female greater one-horned rhinoceros (Rhinoceros unicornis) and her 6-yr-old female offspring by skin biopsy, intradermal skin testing (IDST), and allergen-specific serum IgE testing. Dam and offspring presented with seasonal, erosive, and ulcerative dermatitis affecting the face, legs, and trunk starting at 6 and 2 yr of age, respectively. IDST was performed at the caudal pinnal base using 61 regionally specific allergens. Specific serum allergen responses were detected using Heska's Equine ALLERCEPT^® Allergen Panel. Histopathology of the lesions was consistent with an allergic etiology. Injectable allergen-specific immunotherapy was initiated in both animals and within 6 to 18 mon after commencing hyposensitization clinical improvement was noted. This report documents a repeatable methodology for IDST and serological allergen testing for use in rhinoceroses. The hyposensitization protocol detailed here can help guide future treatment protocols.

The Patterns and Causes of Dermatitis in Terrestrial and Semi-Aquatic Mammalian Wildlife

Causative disease and stress agents which manifest as dermatitis in mammals have varying effects on individual animals, from benign irritation and inflammation, to causing morbidity and even mortality. Bacteria, viruses and ectoparasites are all potential causes of dermatitis, and it can be exacerbated by various environmental, genetic and social factors. Furthermore, it is uncertain whether dermatitis is more likely to manifest in already-vulnerable wildlife species. Here, we systematically review the literature for reports of dermatitis in terrestrial and semi-aquatic wild mammalian species, with the goal of determining the biogeographical scale of dermatitis reports, the causes of dermatitis, and whether manifestation of dermatitis is reported more commonly in certain wildlife species or their captivity status (i.e., free-living, in captivity or in a laboratory). We reveal biases in the reporting of dermatitis by a biogeographic realm, with 55% of cases reported in the Nearctic, and towards particular orders of mammals, namely Artiodactyla and Carnivora. Overall, free-living wildlife is almost twice as likely to be reported as having dermatitis than individuals in captivity and six times more likely than individuals in laboratories, which we interpret as owing to exposure to a broader spectrum of parasites in free-ranging individuals, and potential reporting bias in captive individuals. Notably, dermatitis was reported in 23 threatened species, with some species more likely than others to be reported exhibiting clinical signs of dermatitis resulting from underlying health problems. We also find that threatened species are more likely to be reported as having dermatitis in captivity, particularly outside of their endemic home range. This review highlights diverse patterns of dermatological disease causes in captive and free-ranging wildlife, conditions under which they are more likely to be documented, and the need for cross-disciplinary research to ascertain (and so better manage) the varied causes.

Increased inflammation and decreased insulin sensitivity indicate metabolic disturbances in zoo-managed compared to free-ranging black rhinoceros (Diceros bicornis)

Black rhinoceros (rhinos) living in zoos express a host of unusual disease syndromes that are associated with increased morbidity and mortality, including hemolytic anemia, rhabdomyolysis, hepatopathy and ulcerative skin disease, hypophosphatemia and iron overload. We hypothesized that iron overload is a consequence and indicator of disturbances related to inflammation and insulin/glucose metabolism. The objectives of this study were to: (1) generate the first baseline information on biomarkers of inflammation (tumor necrosis factor alpha [TNFα], serum amyloid A [SAA]), insulin sensitivity (insulin, glucose and proxy calculations of insulin sensitivity), phosphate and iron stores (ferritin) using banked serum from free-ranging black rhinos; and (2) then compare serum biomarkers between zoo-managed (n=86 individuals) and free-ranging (n=120) animals. Enzyme immunoassays were validated for serum and then biomarker levels analyzed using mixed models while controlling for sex, age and year of sample collection. Concentrations of TNFα, SAA, insulin and insulin-to glucose ratio were higher (P<0.05) in black rhinos managed in ex situ conditions compared to free-living counterparts. Findings indicate that the captive environment is contributing to increased inflammation and decreased insulin sensitivity in this endangered species.

Male reproductive success is correlated with testosterone in the eastern black rhinoceros (Diceros bicornis michaeli)

Among natural populations of polygynous species, males often vary in their lifetime reproductive success. However, in managed populations of endangered species, either in situ or as part of captive breeding programmes, it is important to understand why differences in reproductive success occur. The European captive population of the critically endangered eastern black rhinoceros is currently under-performing relative to their wild counterparts, with low reproductive output and high reproductive skew limiting growth and genetic diversity. To investigate why over 40% of captive males fail to breed, faecal samples were collected weekly from 23 males at 12 institutions across Europe for 4-32 months. Testosterone metabolite concentration was compared between proven and non-proven males and a number of intrinsic and extrinsic factors that could influence reproductive success were also investigated. Males that sired within the last 3½ years had significantly higher androgen concentrations than non-proven males, and average testosterone was positively correlated with the number of offspring sired per year spent in the reproductive age class. Proven and non-proven males did not differ in their body condition, or in average faecal glucocorticoid concentration. Differences in individual temperament were associated with adrenal activity, but did not correlate with reproductive category. Highest testosterone concentrations were observed in proven males that were housed with females during oestrus, and lowest concentrations in non-proven females not housed with females at all during the study period. Further work is necessary to determine whether proven males had higher testosterone due to underlying differences associated with quality, or whether external stimuli such as access to females could influence testosterone concentration and increase a male's chances of becoming a successful breeder.

Superficial necrolytic dermatitis in a dog with an insulin-producing pancreatic islet cell carcinoma

A 10-year-old dog presented with convulsive crisis and symmetrical hyperkeratotic cutaneous lesions affecting the abdomen, inguinal area, eyelids, muzzles, both pinnae, and all the paw pads. Hypoglycemia and hyperinsulinemia were the main biochemical findings. A mass 2 cm in diameter was detected within the left pancreatic lobe by ultrasonography. It was surgically removed and histologically and immunohistochemically diagnosed as an insulin-producing pancreatic islet cell carcinoma. The animal was eventually euthanized due to lack of clinical improvement. At necropsy, metastatic nodules were observed in the pancreatic lymph nodes and liver. Histopathological findings of cutaneous lesions were highly suggestive of superficial necrolytic dermatitis and were interpreted as a paraneoplastic syndrome derived from the islet cell carcinoma. To the authors' knowledge, this is the first report of superficial necrolytic dermatitis associated with an insulin-producing pancreatic neuroendocrine carcinoma in dogs.

Review of laboratory and necropsy evidence for iron storage disease acquired by browser rhinoceroses

Necropsies of two browser rhinoceroses, African black (Diceros bicornis) and Sumatran (Dicerorhinus sumatrensis), often reveal extensive iron-pigment deposition in various tissues. This condition (hemosiderosis) has not been observed in species that are natural grazers, African white (Ceratotherium simum) and Asian greater one-horned (Indian; Rhinoceros unicornis), nor in any species free ranging in the wild. The causes, clinical significance, and consequences of captivity-acquired hemosiderosis have remained controversial despite two decades of compelling evidence that iron tends to accumulate logarithmically in all members of affected species in proportion to periods of expatriation; total-body iron loads can reach 10-fold in less than 3 yr and eventually exceed reference ranges by two to three orders of magnitude; iron overburdens are accompanied by laboratory and histopathologic evidence of cellular injury, necrosis and other clinical consequences characteristic of chronic pathologic iron storage [corrected] disorders (ISD) in humans and other species (hemochromatosis); and that ISD develops in many other exotic wildlife species displaced from their natural habitats. The historical evolution of evidence establishing the development of pathologic ISD in browser (but not in grazer) rhinoceroses and the possible relevance of ISD to other conditions affecting these two species will be reviewed. Evidence reviewed includes new as well as published data derived from quantitative measurements of iron analytes in sera and necropsy tissues and histopathologic evaluations of current and past necropsies of captive and free-ranging rhinoceroses of all four available species. The evolutionary, husbandry, and conservation implications of ISD in rhinoceroses are relevant to understanding ISD acquired by many other species of exotic wildlife when displaced from their natural environments.

Hypoaminoacidemia is not associated with ulcerative lesions in black rhinoceroses, Diceros bicornis

Ulcerative oral and skin lesions have become an issue of concern for the health of the managed black rhinoceros (rhino) (Diceros bicornis) populations. Lesions exhibited by the black rhino are clinically similar to those observed in other species with superficial necrolytic dermatitis (SND). One biochemical alteration in dogs with SND is severe hypoaminoacidemia, and nearly all cases are fatal. The objective of this study was to determine if black rhinos with analogous lesions exhibit a similar hypoaminoacidemia. Amino acid concentrations were measured in monthly plasma samples collected for 1 yr from black rhinos with (n = 4) and without (n = 34) lesions clinically consistent with SND. The rhinos with skin and/or oral lesions were zoo born males, ages 2, 6, 17, and 23 yr, from four different facilities. Three rhinos recovered from skin (n = 2) and oral lesions (n = 1). However, the one male with both skin and oral lesions died with the disease. None of the affected black rhinos exhibited a decrease in any of the amino acids evaluated or for total amino acid concentrations (P > 0.05). Based on the absence of hypoaminoacidemia and the comparatively low mortality rate in rhinos with lesions, it appears that this syndrome is not entirely consistent with SND observed in other species. These data will be useful for future assessments of rhino nutritional status and other potential metabolic diseases.

A potential link between phosphate and aging--lessons from Klotho-deficient mice

Phosphate homeostasis is maintained primarily by a bone-kidney endocrine axis. When phosphate is in excess, fibroblast growth factor-23 (FGF23) is secreted from bone and acts on kidney to promote phosphate excretion into urine. FGF23 also reduces serum vitamin D levels to suppress phosphate absorption from intestine. Thus, FGF23 functions as a hormone that induces negative phosphate balance. One critical feature of FGF23 is that it requires Klotho, a single-pass transmembrane protein expressed in renal tubules, as an obligate co-receptor to bind and activate cognate FGF receptors. Importantly, defects in either FGF23 or Klotho not only cause phosphate retention but also a premature-aging syndrome in mice, which can be rescued by resolving hyperphosphatemia. In addition, changes in extracellular and intracellular phosphate concentration affect glucose metabolism, insulin sensitivity, and oxidative stress in vivo and in vitro, which potentially affect aging processes. These findings suggest an unexpected link between inorganic phosphate and aging in mammals.

Klotho

The klotho gene was identified as an "aging-suppressor" gene in mice that accelerates aging when disrupted and extends life span when overexpressed. It encodes a single-pass transmembrane protein and is expressed primarily in renal tubules. The extracellular domain of Klotho protein is secreted into blood and urine by ectodomain shedding. The two forms of Klotho protein, membrane Klotho and secreted Klotho, exert distinct functions. Membrane Klotho forms a complex with fibroblast growth factor (FGF) receptors and functions as an obligate co-receptor for FGF23, a bone-derived hormone that induces phosphate excretion into urine. Mice lacking Klotho or FGF23 not only exhibit phosphate retention but also display a premature-aging syndrome, revealing an unexpected link between phosphate metabolism and aging. Secreted Klotho functions as a humoral factor that regulates activity of multiple glycoproteins on the cell surface, including ion channels and growth factor receptors such as insulin/insulin-like growth factor-1 receptors. Potential contribution of these multiple activities of Klotho protein to aging processes is discussed.

A review of some of the health issues of captive black rhinoceroses (Diceros bicornis)

In captivity, black rhinoceroses (Diceros bicornis) are beset by many disease syndromes not described in black rhinoceroses in the wild. Hemolytic anemia, hepatopathy, and ulcerative dermatopathy that lead to increased morbidity and mortality characterize these syndromes. It is uncertain whether these are separate disease syndromes with different etiologies or the same disease with different manifestations. This article offers a brief review of some of the health issues of concern for the captive black rhinoceros population and proposes some possible avenues of research for consideration.

Corticosteroid-induced suppression of in vitro lymphocyte proliferation in four captive rhinoceros species

Captive African black rhinoceroses (Diceros bicornis) are unusually susceptible to several diseases not commonly observed in any of the other three rhinoceros species maintained in captivity. The potential role of corticosteroids (either endogenously produced or exogenously administered) in the development of these sometimes fatal diseases has been questioned. In this study, the suppressive effects of two therapeutic corticosteroids (dexamethasone and hydrocortisone) on in vitro lymphocyte proliferation was examined in four rhinoceros species, including the Sumatran rhinoceros (Dicerorhinus sumatrensis, n = 3), Indian rhinoceros (Rhinoceros unicornis, n = 4), African black rhinoceros (n = 10), and African white rhinoceros (Ceratotherium simum, n = 5). Three blood samples collected from each rhinoceros 1 mo to 1 yr apart provided replicates for the study. Both dexamethasone and hydrocortisone suppressed (P < 0.05) lymphocyte proliferation stimulated by B-cell mitogens (pokeweed and lipopolysaccharide) and T-cell mitogens (phytohemagglutinin and concanavalin A). Suppressive effects of the glucocorticoids differed (P < 0.05) depending on the mitogen used to stimulate the lymphocytes. Overall, dexamethasone was a more potent suppressor of cell proliferation when compared with hydrocortisone (P < 0.05). However, black rhinoceros cell proliferation in response to any of the four mitogens was never completely suppressed, even in cultures containing the highest steroid concentration tested (10(-3) M). The effect of the two corticosteroids differed slightly among the rhinoceros species and subspecies tested, but there was no evidence that eastern or southern black rhinoceros lymphocytes were more sensitive to the suppressive effects of corticosteroids than the other rhinoceros species.

Successful treatment of a squamous cell carcinoma in a white rhinoceros, Ceratotherium simum

A captive 33-year-old male white rhinoceros with seasonal dermatitis was diagnosed with a malignant squamous cell carcinoma on the right flank. Staphylococcus aureus was cultured from the skin lesions. No fungal or yeast was isolated. The dermatitis was treated with a combination of oral antibiotics (trimethoprim-sulphadiazine) and topically with weekly chlorhexidine washes and a mixture of a zinc oxide, balsam peru and bismuth oxide cream. Under azaperone and butorphanol anaesthesia, the skin tumour was surgically removed. The tumour was excised with wide margins and allowed to heal by secondary intention as primary wound closure was not possible. A post-mortem performed 2 years later for an unrelated condition revealed no metastases or recurrence of the skin tumour. It was presumed that chronic irritation or trauma may have contributed to the development of the skin tumour. This is the first detailed report of the successful treatment of a squamous cell carcinoma not associated with the horn in a rhinoceros.

Metabolic epidermal necrosis in a dog associated with pancreatic adenocarcinoma, hyperglucagonaemia, hyperinsulinaemia and hypoaminoacidaemia

A case of metabolic epidermal necrosis associated with a pancreatic carcinoma is described. Normoglycaemia, reduced serum fructosamine, and hypoaminoacidaemia were identified. Hyperinsulinaemia and hyperglucagonaemia were documented. Immunohistochemistry documented strong tumour expression of both insulin and glucagon supporting combined paraneoplastic production of both hormones by the tumour. Enteral protein and fatty acid supplementation and parenteral amino acid supplementation proved ineffective. Metastasis to regional lymph nodes was identified and the patient was euthanased.

Comparative studies of mitogen- and antigen-induced lymphocyte proliferation in four captive rhinoceros species

Cellular immune function in four rhinoceros species was evaluated by way of in vitro lymphocyte proliferation responses to mitogenic and antigenic stimuli to establish normative data on white blood cell activity for each species and to identify species-specific differences that might help explain the predisposition of black rhinoceroses (Diceros bicornis) to disease. A cross section of the U.S. rhinoceros population encompassing all four captive species was sampled, including the Sumatran rhinoceros (Dicerorhinus sumatrensis) (n = 3); Indian rhinoceros (Rhinoceros unicornis) (n = 4); African black rhinoceros (n = 16); and African white rhinoceros (Ceratotherium simum) (n = 10). Of the four species evaluated, African black rhinoceroses exhibited the weakest (P < 0.05) lymphocyte proliferative responses to the mitogens: pokeweed (0.1 microg/ml), phytohemagglutinin (0.3 microg/ml), and concanavalin A (5.0 microg/ml). Total cell density at the end of culture was only 70% of that achieved with lymphocytes isolated from African white rhinoceroses, Indian rhinoceroses, and Sumatran rhinoceroses. However, lymphocyte response to bacterial endotoxin lipopolysaccharide was similar (P > 0.05) across species. Antigenic stimulation produced much weaker responses than mitogenic stimulation. No differences (P > 0.05) were observed among rhinoceros species in response to 1 and 10 microg/ml of Leptospira icterohemorrhagiae or Leptospira gryppotyphosa. Lymphocytes from African white rhinoceroses proliferated weakly in the presence of Aspergillus fumigatus filtrate, whereas lymphocytes from the southern black rhinoceros subspecies appeared slightly suppressed in the presence of increasing doses (0.1, 1, and 10 microg/ml) of Aspergillus filtrate. This comparative data set characterizing lymphocyte proliferation in the rhinoceros reveals several differences in immune cell responses among rhinoceros species and provides some evidence that lymphocytes of captive African black rhinoceroses are less vigorous than those of the other rhinoceros species.

The stress response to environmental change in captive cheetahs (Acinonyx jubatus)

The captive North American cheetah (Acinonyx jubatus) population is not self-sustaining because of high prevalences of unusual diseases and poor reproductive success. Cheetahs are commonly moved between zoos for breeding purposes to maintain genetic diversity within the captive population, and movement may exacerbate infertility and disease. Fecal corticoids were analyzed by radioimmunoassay to measure the stress response of cheetahs to movement between facilities. Fecal samples were collected from 15 cheetahs for 14 days before movement and for at least 30 days after movement. For each cheetah, premovement fecal corticoid concentrations were used to determine baseline and then compared with trends in postmovement concentrations. In general, postmovement corticoid concentrations either increased (n = 8), did not change (n = 2), or decreased (n = 5). Although individual animal differences occurred, corticoid concentrations increased for most animals moved on-exhibit and decreased in animals moved off-exhibit. Animals moving on-exhibit had an 18-times greater risk of having corticoids elevated more than two standard deviations above baseline for 30 days after movement compared with animals that moved off-exhibit. In addition, greater day-to-day variation in corticoids occurred in animals moved on-exhibit. In general, animals with initially low baseline corticoid concentrations had a greater postmovement corticoid response than cheetahs with initially high baseline levels. These results indicate that some cheetahs have a prolonged stress response when moved between facilities, and the magnitude and character of this response is influenced by the exhibit environment.

Oral, nasal, and cutaneous eosinophilic granulomas in the black rhinoceros (Diceros bicornis): a lesion distinct from superficial necrolytic dermatitis

Oral, nasal, and cutaneous lesions resembling eosinophilic granulomas (EGs) were observed in eight captive black rhinoceroses (Diceros bicornis). Oral lesions were observed in all affected animals and occurred most often behind the prehensile lip. The typical clinical history of affected animals included oral bleeding or epistaxis from multilobulated, fungating, proliferative masses with areas of ulceration. Histologically, lesions were characterized by prominent infiltrates of eosinophils and rare foci of collagen degeneration on a background of marked submucosal or dermal neovascularization. Mucosal or epidermal hyperplasia was also present sometimes in association with distinctive epithelial degenerative changes consistent with superficial necrolytic dermatopathy of black rhinoceroses. Lesions of EG and superficial necrolytic dermatopathy were interpreted as being concurrently manifested in these cases. EG lesions spontaneously resolved over periods of 30 days-7 mo and were recurrent in three animals. Lesions were responsive to treatment with corticosteroids or to local cryotherapy with liquid nitrogen. Two animals treated with systemic corticosteroids died of disseminated fungal infections, emphasizing that corticosteroids should be used cautiously in black rhinoceroses.

Clinicopathological, ultrasonographic, and histopathological findings of superficial necrolytic dermatitis with hepatopathy in a cat

This report describes the antemortem diagnosis and antemortem and postmortem findings of superficial necrolytic dermatitis with hepatopathy (i.e., hepatocutaneous syndrome) in a cat. A 5-year-old Maine coon was evaluated because of a history of pruritic alopecia and liver enzyme elevations. Abdominal ultrasonography revealed a reticular pattern to the hepatic parenchyma. Histopathological findings of the liver were nodular regeneration with bands of vacuolated hepatocytes and bile duct hyperplasia, characteristic of the hepatopathy frequently associated with superficial necrolytic dermatitis. Skin histopathology revealed multifocal parakeratosis, midepidermal spongiosis, and basal cell hyperplasia consistent with superficial necrolytic dermatitis.

Plasma amino acid concentrations in 36 dogs with histologically confirmed superficial necrolytic dermatitis

Plasma amino acid concentrations were measured in 36 dogs diagnosed with superficial necrolytic dermatitis (SND) via skin biopsy. The median age of the dogs was 10 years, and 27 out of 36 (75%) were male. Twenty-two out of 36 (61%) of the dogs were accounted for by six breeds; West Highland white terriers (six), Shetland sheepdogs (five), cocker spaniels (four), Scottish terriers (three), Lhasa apsos (two) and Border collies (two). The mean concentration (+/- standard deviation) was calculated for each measured plasma amino acid and compared to previously documented concentrations of plasma amino acids measured in dogs with acute and chronic hepatitis. The ratio of branched chain amino acids to aromatic amino acids in the dogs with SND was 2.6, slightly lower than that in normal dogs. The mean plasma amino acid concentrations for dogs with SND were significantly lower than for dogs with acute and chronic hepatitis. A metabolic hepatopathy in which there is increased hepatic catabolism of amino acids is hypothesized to explain the hypoaminoacidaemia seen in SND.

Metabolic epidermal necrosis-hepatocutaneous syndrome

It is clear that cutaneous lesions of metabolic epidermal necrosis in the dog can occur either with a demonstrable glucagon-secreting tumor or with hepatic disease without any detectable glucagonoma. Additional clinical case reports of the disease in cats are needed to better characterize the disease in this species. The lesions of NME-MEN may not represent a specific physiological mechanism of cutaneous disease but instead a pathophysiological process that can be triggered by several systemic metabolic abnormalities. The fact that NME is observed in association with a variety of conditions supports the theory that an overall metabolic derangement results in the rash. The prognosis for canine MEN is poor; however, some affected dogs have been maintained for many months with dietary management. High-quality protein diets such as Hill's Prescription Diet a/d (Hill's Pet Products) or other "recovery" diets may be helpful. Zinc and essential fatty acid supplementation may help some patients. Dietary supplementation with cooked egg yolks may be helpful. It is prudent to avoid corticosteroids in these cases, as development of diabetes mellitus worsens the prognosis. Histopathological examination of the pancreas coupled with determination of plasma glucagon may help define the characteristics of GS versus HS in dogs. It is possible that some dogs diagnosed with MEN-HS may have an undetected pancreatic tumor. Although the hepatic ultrasound findings in dogs with MEN-HS are becoming well characterized, it is possible for dogs with pancreatic neuroendocrine tumors to also have abnormal hepatic ultrasonography. As the presence of MEN and hepatic disease does not necessarily rule out the presence of a pancreatic tumor, prospective studies correlating plasma glucagon levels with pancreatic histopathology in cases of MEN-GS versus MEN-HS seem warranted.